Q7 of 95 Page 94

Give a reason, why a matured mammalian erythrocyte lacks nucleus and mitochondria?

A matured mammalian erythrocyte lacks nucleus & mitochondria as loss of nucleus makes the RBC biconcave thus increasing the surface area for absorbing more oxygen. On the other hand, loss of mitochondria does not allow the RBC to utilize oxygen for themselves.

*Note: Mitochondria are the sites for cellular respiration.


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5

Complete the following statements by filling in the blanks from the choices given in the brackets.

(a) The blood vessel that begins and ends in capillaries is the ………………… (hepatic artery, hepatic portal vein, hepatic vein).


(b) A blood vessel which has small lumen and thick wall is …………. (capillary, lymphatic duct, artery, venule)


(c) The valve which prevents back flow of blood in the veins and lymph vessels…… (mitral valve, tricuspid valve, semilunar valve).

 6

Note the relationship between the first two words and suggest the suitable word/words for the fourth place:

(a) Lubb : Atrioventricular valves :: Dup : ………………………………..


(b) Coronary artery : Heart :: Hepatic artery: ………………..

 1

What does the term "double circulation" mean?

 2

When are the sounds "LUBB" and "DUP" produced respectively during heart beat?